Lighting fitting for a u-shaped gas discharge lamp

ABSTRACT

A lighting fitting which comprises a preferably U-shaped gas discharge lamp in which the space above the lamp is covered by a trough-shaped mirror, and a refractor plate and a reflector are arranged on either side of the lamp. This lighting fitting provides a street surface illumination the intensity of which varies uniformly over a wide area on either side of the elongate light source.

United States Patent [191 Rijnders LIGHTING FITTING FOR A U-SHAPED GAS DISCHARGE LAMP [75] Inventor: Johannes Rijnders, Emmasingel,

Eindhoven, Netherlands [73] Assignee: U.S. Philips Corporation, New

York, NY.

22 Filed: Dec. 1,1971

21 Appl. No.: 203,568

[30] Foreign Application Priority Data Dec. I7, 1970 Netherlands 7018379 [52] US. Cl 240/25, 240/l 1.4 R, 240/5l.1l R, 240/93 [51] Int. Cl F218 3/02 [58] Field of Search 240/25, 51.11, 11.4, 240/93 [5 6] References Cited UNITED STATES PATENTS 2,878.369 3/1959 Rijnders 240/25 [11] 3,775,605 [451 Nov. 27, 1973 4/1'959 Rijnders .f. 240/25 1/1945 Roberts 240/5l.ll X

Primary Examiner-Samuel S. Matthews Assistant Examiner-Kenneth C. Hutchison Attorney-Frank R. Trifari [5 7] ABSTRACT A lighting fitting which comprises a preferably U- shaped gas discharge lamp in which the space above the lamp is covered by a trough-shaped mirror, and a refractor plate and a reflector are arranged on either side of the lamp. This lighting fitting provides a street surface illumination the intensity of which varies uniformly over a wide area on either side of the elongate light source.

4 Claims, 2 Drawing Figures I AVmV/AVAVAVAVAVAVAVAVA\7/AV/7 PAIENTEI] NW2 7 I875 Fig.2

INVENTOR. JOHANNES RIJNDERS AGENT LIGHTING FITTING FOR A U-SI-IAPED GAS",

DISCHARGE LAMP 1 The invention relates to a lighting fitting for two elongate light sources extending parallel to' each other, preferably a U-shaped gas discharge lamp, in whichthe longitudinal dimension of the lamp extends-parallel to a street surface to be illuminated, and the light intensity, calculated from the street surface directly below the lighting fitting to that place of the street surface where thelight rays impinge upon said street surface at a more acute angle, increases. Such a lightingfitting. is

often needed when a constant brightness is required over a very wide illumination area. Thisrequiresthe light intensity experienced at larger distances on the side of the light beam radiating downwards directly to be very considerable.

The invention provides a lighting fitting which meets the said need.

For that purpose the lighting fitting according to the invention is characterized in that the lighting fitting is constructed to hold the lamp in the operatingcondition in such manner that the plane containingthe limbs of the lamp is transverse to the street surface to be illuminated. A reflector is arranged on either side of said plane, and a refractor is present between the lamp and the reflector; the part of the reflector'closer to the street surface to be illuminated reflects the light rays of i the limb closer to the street inan unrefractcd mannerand reflects the light rays originating from the other limb in a refracted'manner. The upperpart only reflects the refracted light rays originating from the two limbs, and the reflector is shaped'so that the unrefracted reflected light rays impinge farther from the lighting fitting than the refracted reflected light rays.

In order to fulfil the object mentioned in the.- preamble, the lighting fitting provides a reflectorsystem of which the lower part mainly supplies a sharp beam of directly reflected light'which is directed to larger distances from the lighting fitting. The uppermost part of the reflector in principle reflects only refracted'light which thus produces a smaller intensity of reflected radiation. This light impinges mainly between the previously mentioned beam and the light beam straightbelow the lamp. Together with the higher impinging radiation reflected by the trough-shaped mirror it isachieved that a very gradually increasing light intensity is obtained from directly below the lighting fitting to larger distances outside the lighting fitting; The light intensity of said fitting therefore varies very uniformly over a large illumination area.

The use of refractor plates on either side of the lamp is known per se albeit that in known systems said plates comprise one or more prismatic systems which deflect light beams but by no means scatter as is the-case in the lighting fitting according to the invention.

It is also known per se to arrange a trough-shapd mir-' ror above a U-shaped gas discharge lamp, albeit that the plane comprising the two limbs of the lamp is not arranged transverse to the street surface butparallel thereto. The effect of the trough-shaped mirror then is less characteristic.

In order that the invention may be readily carried into effect, one embodiment thereof will now be described in greater detail, by way of example, with reference to the accompanying drawing, in which FIG. 1 is a cross-sectional view of the lighting fitting and FIG. 2 shows the illumination resultin a polar di-agram. t

The lighting fitting according to the invention comprises a U-shaped gas discharge-lamp which is'incorporated in a frameand the limbs of which-are denoted by l' and 3; The frame comprises a-plate 5which is reflecting-on its lower side and which has the curved reflector members7; the curvature of said. reflector members is substantially parabolic; F is the focus.

Furthermore are present a set of refractor plates 9 extending on either side of the lamp. On their upper side said plates have coarse ribsand towards the street surface l0ythey have ever finer ribs. A trough-shaped mirror, in this case a V-shaped'mirror 11, is arranged above the lamp.

The drawing only shows the cross-sectional view. The lighting fitting shown is elongate viewed in a direction transverse to the .plane of the drawing.

The effect of this so-called broad. beam lighting fitting having a constant illumination level throughout its illumination width is as follows.

The rays 13 which are directed downwards immediately supply a beam which is denoted by 15in the polar diagram shown in FIG. 2.

The rays 17 emerginglaterally' from the lower limb lcan directly impinge upon the part 19 of the reflector 7'and due to the parabolic shape of said reflector they are reflected'substantially parallel to each other (ray 21); they produce a beam 23'the brightness effect of which is large at'a great distance from the lighting fitting. The rays 26 which emerge from the lower limb 1- and first impinge upon the refractor plate 9 and then on the reflector 7 are scattered and, after'reflection ray 28) by the part 35 of the reflector 7, are reflected with a'reduced intensity; the rays originatingfrom said'part impinge in the beam area 39 (see FIG. 2).

The rays 27 emerging from the upper limb 3 after refraction by refractor 9 impinge upon the reflector plates 7'; they will be scatteredmore strongly (rays 29, 31, 33); the rays collectively impinging upon the reflectorpart'35 after refraction (rays 37) produce a beam 53of'low intensity (see FIG. 2).

The V-shaped mirror 11- forms as it werefour'apparentlight sources of which only two are sh'own in FIG.

1.- The light rays 36 emerging upwards from the two limbs l and 3 of the lamp are thrown, afterreflection by the V-shaped mirror, against therefractor plates 9, scattered there (see-rays 47, 49, 51) and ultimately reflected with reduced intensity by the reflector 7 to the part of the'street surface 10 just below the'lighting fitting. They together contributeadditionally to the formation of beam 53.

When the beams 15, 23, 39, 53 in FIG. 2 are united it is found that an illumination pattern is formed the illumination level of which is very uniform over alarge width. The light intensity increases according as the light rays are directed to farther distances from the lighting. fitting.

The. scattering effect of the refractor plates 9-decreases in a downward direction. As a result of this the light rays originating from the upper limb are scattered more strongly than light rays originating from thelower limb. This again contributes to a better light distribution in said beam pattern.

What is claimed is:

1. A lighting arrangement comprising a lighting fitting and two elongate lightsources within said fitting.

and extending parallel to each other, such as a U- shaped discharge lamp having two parallel legs, said lighting fitting comprising:

means for holding said elongated light sources in a plane which is transverse to a surface to be illuminated;

a reflector, having an upper plate and at least one side plate of predetermined concave shape, the upper plate extending parallel to the surface to be illuminated and superposed above the light sources, the upper and side plates having inner surfaces adapted to reflect light cast from said light sources; and

a refractor, said refractor being positioned adjacent to the light sources in a plane parallel to the light sources and between the light sources and the side plate, said refractor being affixed to the upper plate and extending to a point adjacent to the lower light source, said refractor adapted to refract light directed from said upper light source toward the side plate of said reflector without substantially refracting light directed from said lower light source toward the side plate of the reflector, said refractor also adapted to refract light directed from both upper and lower light sources toward the upper plate of the reflector.

2. The lighting fitting of claim 1 wherein the predetermined concave shape of the inner surface of the side plate of the reflector is a portion of a parabola.

3. A lighting fitting as claimed in claim 1 wherein the refractor includes means to scatter light, said means scattering light by an amount which decreases as a function of the distance from the upper plate.

4. A lighting fitting as claimed in claim 1 also comprising a second refractor, both being shaped as flat plate refractors, said refractors being situated on either side of the plane passing through the light sources and approximately symmetric about said plane, and also comprising a second concave side plate having an inner reflecting surface, said side plates being approximately equidistant from the plane of the light sources, and wherein a V-shaped mirror is positioned above the light sources and between the refractors, the mirror having side edges which abut the refractor edges adjacent to the upper plate, the apex of the V being directed toward the light sources. 

1. A lighting arrangement comprising a lighting fitting and two elongate light sources within said fitting and extending parallel to each other, such as a U-shaped discharge lamp having two parallel legs, said lighting fitting comprising: means for holding said elongated light sources in a plane which is transverse to a surface to be illuminated; a reflector, having an upper plate and at least one side plate of predetermined concave shape, the upper plate extending parallel to the surface to be illuminated and superposed above the light sources, the upper and side plates having inner surfaces adapted to reflect light cast from said light sources; and a refractor, said refractor being positioned adjacent to the light sources in a plane parallel to the light sources and between the light sources and the side plate, said refractor being affixed to the upper plate and extending to a point adjacent to the lower light source, said refractor adapted to refract light directed from said upper light source toward the side plate of said reflector without substantially refracting light directed from said lower light source toward the side plate of the reflector, said refractor also adapted to refract light directed from both upper and lower light sources toward the upper plate of the reflector.
 2. The lighting fitting of claim 1 wherein the predetermined concave shape of the inner surface of the side plate of the reflector is a portion of a parabola.
 3. A lighting fitting as claimed in claim 1 wherein the refractor includes means to scatter light, said means scattering light by an amount which decreases as a function of the distance from the upper plate.
 4. A lighting fitting as claimed in claim 1 also comprising a second refractor, both being shaped as flat plate refractors, said refractors being situated on either side of the plane passing through the light sources and approximately symmetric about said plane, and also comprising a second concave side plate having an inner reflecting surface, said side plates being approximately equidistant from the plane of the light sources, and wherein a V-shaped mirror is positioned above the light sources and between the refractors, the mirror having side edges which abut the refractor edges adjacent to the upper plate, the apex of the V being directed toward the light sources. 